Wireless Networks: Personal, Local, Metropolitan

Speedups, Security, Power

John Schafer

University of Michigan

Ann Arbor CSG

10 May 2000

jbs@umich.edu

www.itcom.itd.umich.edu/wireless/

Overview

• Current choices• Speedups coming• Power over Ethernet• Authenticated Wireless• Wireless Personal Area Network: Bluetooth• Point-to-point Wireless Metropolitan Area

Networking

Terminology

• Access point (AP), station adapter• WEP (Wired Equivalent Privacy)

– Encryption of data packets, 40 or 128 bit

• Access control table - list of MAC addresses• Speeds are nominal, throughput is about one half

Current ChoicesStandard Speed

(Mbps)Power*(mA)

Range(feet)

Cost

OpenAir (Proxim) 1.6 5/300 150 $250

HomeRF 1.6 5/300 150 $150

IEEE 802.11Frequency Hopping

2 10/300 150 $150

IEEE 802.11bDirect Sequence

11 10/300 150 $100

Bluetooth (802.15) 1 .03/30 30 $30

*sleep/transmit

Speedups Coming

High SpeedWLANs

IEEE802.11b

IEEE802.11a

HIPERLANType 1

HIPERLANType 2

Band, GHz 2.4 5 5 5

Channels 3 5 7Data Rates,

Mbps

1, 2,

5.5, 11

6, 9, 12,

18, 24,54

6, 12, 24 20-54

Modulation CCK OFDM GMSK OFDMStandard

ratified

4Q99 Due 4Q00 Sep-96 Due 4Q99

Productsavailable

4Q99 2001 4Q00 2002

Speedups of questionable value

• HiperLAN1– Only one vendor with plans, wait for HiperLAN2 or

802.11a

• 22 Mbps 802.11b– First meeting May 8-12, 2000

– Skip it and wait for 802.11a, 54 Mbps

• 10 Mbps Frequency Hopper (IEEE 802.11)– Needs FCC rule change, seems unlikely

Power over Ethernet

• Conduit to power AP: $800, Enet: $300• Several methods being discussed (IEEE)

– Use spare wire pairs on CAT5 cable

– Couple DC power on signal pairs

• Smart - only turn on power to responsive device• Applications - VoIP phones, Security, AP’s• Built into future switches/hubs• Standard due 3Q2001

Problems with current security

• Encryption keys set the same for all users• Password for network given to all users• Access control table updated manually• Access control based on MAC address - spoofable

Authenticated Wireless

• Radius client in access point• IEEE 802.1x is working on a standard• Lucent first to market ahead of standard

Lucent Access Server AS-1000

• Diffie-Hellman key exchange– Per user, per session key used for WEP encryption

• Setup PPP link• RADIUS client in AP - RADIUS servers -

Kerberos• Limitations:

– First version - No Roaming

– User must exist in authentication system before first connection

Merit RADIUS system, ABS, PTS

• State-wide: 800 modem pools, 160 RADIUS servers

• Accounting and Billing System (ABS)• Protection Server (PTS)• AS-1000 looks like a modem pool• Auto-subscribe, monthly billing, usage charges,

grant access based on PTS groups

Adapting IEEE 802.1x to 802.11

• Based on existing standards– Extensible Authentication Protocol (EAP)

– RADIUS

• Dynamic key management• Roaming - handoff of keys to AP• Unauthenticated VLAN support - access to

registration/enrollment server (optional)• Expected Summer 2001• http://grouper.ieee.org/groups/802/1/index.html

Bluetooth

• Wireless Personal Area Network (PAN)• IEEE 802.15• Asynch data and up to 3 voice channels• Data: asymmetric 721 Kbps/57 Kbps, symmetric

432.6 Kbps• Uses same 2.4 GHz band as 802.11• Fast Frequency Hopper, 1600 hops/sec.• Interferes with 802.11 WLANs

Ericsson Bluetooth Module

Bluetooth - Applications

• Replace infrared and custom cables• Computers, PDAs, Palmtops, Mobile phones• Headsets, Digital cameras, Automobiles• Bluetooth SIG has 1400 member companies• Plan to migrate your WLANs to 5 GHz band• http://www.bluetooth.com/• http://www.bluetooth.net/

Wireless Metropolitan Area Nets

• Point-to-point and point-to-multipoint• Unlicensed (2.4 GHz ISM band)

– WLAN hardware plus external antennas

– Speed: 1-5 Mbps, Distance: <20 miles

• Licensed spectrum– Local Multi-point Distribution Service (LMDS)

• FCC auction in spring of 1998, 38 GHz band

• Line-of-site, up to 5 miles, up to 45 Mbps

• Laser